L1 cell adhesion molecule (em>L1CAM) is an integral membrane glycoprotein that mediates intercellular adhesion at the cell surface, and it has been shown to be intimately involved in neural function and development. The em>L1CAM gene is located at Xq28 and contains 28 exons. Various types of mutations in em>L1CAM have been reported in patients with X-linked hydrocephalus, MASA syndrome, type 1 X-linked spastic paraplegia (SPG1), and Hirschsprung disease (Jouet M et al. Am J Hum Genet. 1995;56:1304-1314 and Okamoto N et al. J Hum. Genet. 2004;49:334-337).